Continuous casting apparatus with means supporting only outer portions of non-uniformingot



Oct. 31, 1967 J- BRONDYKE ET AL 3,349,837

CONTINUOUS CASTING PPARATUS WITH MEANS SUPPORTING o OUTER PORTIONS 0FNON-UNIFORM INGOT Filed July 19, 1965 Kennefh Riv/7 BY United StatesPatent Ofilice 3,349,837 Patented Oct. 31, 1967 3,349,837 CONTINUOUSCASTING APPARATUS WITH MEANS SUPPORTING ONLY OUTER POR- TIONS OFNON-UNIFORM INGOT Kenneth J. Brondyke, Oakmont, and Richard T. Craig,

New Kensingtou, Pa., assignors to Aluminum Company of America,Pittsburgh, Pa., a corporation of Pennsylvania Filed July 19, 1965, Ser.No. 472,820 8 Claims. (Cl. 164-474) ABSTRACT OF THE DISCLOSURE In thecontinuous horizontal casting of large fiat metal ingots, e.g. having across section of 16 x 35 inches, the mold opening is concave across thetop and bottom to allow for non-uniform shrinkage. The starting plugemployed in initiating the run must correspond to the concave shape ofthe mold opening although the ingot, by the time it has emerged about afoot, has shrunk to its desired fiat configuration. The support meansmust be care fully aligned to prevent flexing of the ingot axis. If itis aligned with the lowermost portion of the concave mold opening so asto maintain mold alignment for the starting plug, the solidified ingot,when it reaches the support means, is out of alignment and tends tosettle downwardly to the support means thereby flexing the ingot axiswhich, in turn, results in a serpentine appearance along the ingotlength and necessitates excessive scalping and material waste. Thisdifliculty is alleviated if the support means is arranged to supportonly the outermost portion of the ingot width, that is those portions ofthe ingot width where the concavities run-out does not ex ceed 50% ofthe total concavity run-out.

This invention relates to the continuous casting of metal ingots inhorizontaly disposed open ended molds, and especially to casting ingotsof the light metals, alu' minum and magnesium, together with theiralloys.

Horizontal continuous casting of ingots has found commercial acceptancebecause of recognized advantages in certain respects over verticalcontinuous castings. In the horizontal casting under consideration here,molten metal is provided in a reservoir most often separated from anopen ended horizontal mold by a partial barrier having an opening toconduct liquid metal from the reservoir to the drastically chilled moldfrom which the solidifying metal is continuously withdrawn in ahorizontal direction. Means are provided for withdrawing and supportingthe ingot emerging from the mold, and, accordingly, an endless belt, aseries of rollers, or the like, is disposed to bear against the bottomsurface of the ingot. The belt or other support can be powered to servethe dual functions of supporting and withdrawing the ingot.

When casting relatively large ingot, for instance having a cross-sectionof 16" in thickness by 35" in width, a size highly suitable for rollinginto sheet, a non-uniform shrinkage pattern is observed across the ingotcross-section. Referring to FIGURE 1, an ingot 10 cast in a mold havinga rectangular opening 12 will exhibit a concave surface condition 14which necessitates removal of a large amount of metal to provide a flatingot for hot rolling or the like. This non-uniform or disproportionateshrinkage or contraction in the vertical dimension is attributed to anon-uniform heat extraction condition in that more heat is extractedfrom the metal in the outer portions of the ingot width. To compensatefor this condition, the bottom and top surfaces, and sometimes the sidesurfaces, of the mold opening are shaped to provide a concave wallconfiguration as shown in FIGURE 2.

As there shown, the ingot 10 is cast in a mold having concave inside topand bottom surfaces 20 to produce an ingot cross-section 12 which issubstantially flat surfaced.

While the chilled mold is described as open ended, obviously the outletof the mold is always closed against flow of molten metal. At the startof the casting run, a starting plug 74, as shown in FIGURE 3, ofsuitable size and configuration is used to close the mold outlet,generally by being inserted thereinto. The casting run is initiated bypermitting molten metal to fill the mold and withdrawing the startingplug with the solidified, or partially solidified, ingot connectedthereto. A'fter withdrawal of the starting plug, the mold outlet isclosed to the flow of liquid metal by the solidified ingot metal.

In horizontal casting, it is essential that the bottom surface of theingot emerging from the mold be aligned with the supporting surface ofthe belt or roller support, to avoid excessive deflection of the ingotas it reaches and is carried along the supporting surface. Anysignificant deflection here causes a repeating condition to occur in thefreezing ingot which renders the ingot length somewhat wavy orserpentine. This, in turn, necessitates excessive metal removal toprovide the non-wavy ingot surface required for subsequent fabricationsuch as hot rolling. In vertical casting, no such problem arises, sincethe ingot is principally supported on its end. However, in horizontalcasting, a problem .in this respect is encountered in that while thecenter portion of the ingot undergoes a disproportionate shrinkage,desirably compensated for so that the ingot bottom surface issubstantially flat before it reaches the support means, the startingplug maintains its convex protrusion. At the start of the casting run,the starting plug is positioned upon the support means and aligned withthe bottom of the mold to facilitate insertion and withdrawal of theplug. However, the emerging flat bottomed ingot as it reaches thesupporting means has undergone its disproportionate shrinkage andaccordingly its bottom surface is disposed somewhat higher than thesupport means, by an amount equivalent to the concavity of the mold.This misalignment condition results in a wavy or serpentinecharacteristic along the ingot length caused by repetitive freezingingot deflections downwardly to the support means.

The magnitude of the problem is dependent upon the size and shape of theingot cross-section. The relatively large fiat ingot cross-sectionshighly suitable for hot rolling are the most susceptible. FOr instance,an ingot having a crosssection of 16" thick by 35" wide often requires amold concavity approaching for the top and bottom surfaces to producesubstantially flat corresponding ingot surfaces. The waviness resultingfrom the attendant /5". misalignment causes extremely costly metal wastewhen scalping to obtain flat surfaces to be hot rolled.

According to the invention, a unique solution to the problem has beenfound in that the wavy ingot condition caused by the alignment problemis alleviated by supporting only the outermost portions of the startingplug and ingot cross-sections. This solution offers the advantages ofbeing inexpensive and readily provided for in existing facilities.

It is an object of the invention to provide an apparatus forcontinuously casting ingots, using a horizontally disposed chilled moldhaving surfaces allowing for nonuniform ingot shrinkage, to produce asubstantially straight ingot length. Another object is to provideapparatus for the continuous casting of relatively flat surfaced ingotsusing a horizontally disposed, concave surfaced, chilled mold, theresulting ingot exhibiting a substantially straight, wave-free length.

Other objects of the invention will, in part, be obvious and will, inpart, appear hereinafter in this description and drawings in which:

FIG. 1 is a representation of a rectangular mold opening and the ingotcross-section obtained from it,

FIG. 2 is a representation of a concave mold opening and the rectangularingot cross-section obtained from it,

FIG. 3 is an elevation, partially in cross-section, of a horizontalcasting apparatus, and

FIG. 4 is an elevation in cross-section of an embodiment of theinvention.

Suitable apparatus for continuous casting in a horizontally disposedmold is illustrated in FIG. 3 wherein molten metal reservoir 30 isprovided on one side of an insulating barrier or closure 32. On theopposite side of the closure is a horizontally disposed mold 34 which ischilled by suitable cooling means such as water headers 36 provided withholes 38 to permit spraying water 40 against the surfaces of the moldand the ingot emerging therefrom. The arrangement shown in FIG. 3 isonly schematic or representative in this respect. An opening 44 isprovided in closure 32 for passage of liquid metal from the reservoir 30to the chilled mold. The reservoir is enclosed by suitable insulatingmembers 48, and the molten metal surface 31 is maintained at. a higherelevation than that of the emerging ingot, such that any liquid metal 51within the mold 34 is under a positive liquid metal head. Within themold, a relatively thin embryo ingot surface skin 50 is immediatelyformed by the liquid metal as it contacts the drastically chilled moldsurface. This skin thickens as the ingot progresses outwardly from themold. An ideal solidus line 52 is depicted for the center of the ingotwidth. The non-uniform shrinkage effect is not shown. As shown in FIG.3, the ingot 60 may be solidified some time prior to reaching thesupport means which, in this case, consists of an endless belt 64supported by belt rollers 66 and the belt support plate 68. The beltrollers 66 are about 20 to 25" in diameter and spaced about 6 to feetapart. The belt width is most often at least as wide as the ingot. Thedistance between the mold outlet and the initial contact between thebelt and the ingot generally ranges from 10 to 30". If desired, somemeans such as overhead roller 70 may be provided to urge the ingotagainst the ingot support means to assure intimate ingot contact withthe belt. The belt rollers 66 can be powered as by motor 67, so that thebelt performs both the functions of supporting the ingot and withdrawingthe ingot. The power transmission preferably includes a variable speedfeature to allow for the different casting or ingot withdrawal speeds.Another advantage here is that when starting the casting run, thestarting plug is best brought up to the desired casting speed somewhatgradually. Of course, rollers may be used in lieu of belts; the primemover for ingot withdrawal may be something other than the supportmeans, for instance hold down roller 70 may be driven by motor 71.Various schemes here will suggest themselves to those skilled in theart, although the powered belt shown in FIG. 3 has been found to performquite reliably.

As indicated earlier in this description, the ingot support surface ofthe belt must be aligned with the ingot as it reaches the belt to avoidcausing the ingot deflection, but an alignment problem is encountered inthat the bottom surfaces of the ingot and starting plug reach thesupport belt at different elevations. As also indicated earlier, theseverity of the alignment problem in terms of ingot waviness, is relatedto the size and shape of the ingot cross-section. A relatively smallsymmetrical crosssection, such as a 6" square, poses a relatively minorproblem in this respect, although a 6 thick by 30 wide section may havea misalignment equal to dimension x in FIGURE 2, of V1". Generallyspeaking, the misalignment between the emerging ingot and the supportmeans is not critical so long as it is significantly less than A".However, as the condition approaches Ma" and increases,

such results in the ingot exhibiting a waviness condition which isconsidered excessive from a commercial standpoint. The simplest way tocorrelate the extent of misalignment with the apparatus employed is toconsider the misalignment approximately equal to the total concavitydimension x, in FIG. 2, of the bottom surface of the mold opening andaccordingly the invention will be described in this manner. Thus, theinvention is concerned with the condition where mold bottom surfaceexhibits a substantial concavity, but more particularly where thisconcavity is A" or more, and especially where it is A" or greater, inwhich case the resulting ingot waviness can cause extremely costly metalscrap losses.

The solution to the alignment problem in accordance with the inventioncontemplates supporting both the starting plug and the -ingot connectedthereto only at the outer portions of their respective widths. Such canbe accomplished by the provision of two narrow belts in lieu of thesingle wide belt 64, or the positioning of two such belts upon anexisting single belt. For instance, referring to FIG. 4, thesubstantially fiat-bottomed ingot 60 is supported only on the outer.portion of its width by narrow belts 65, as is also the starting plug74. A practical limit in accordance with the invention is that the ingotand starting plug not be supported by more than that part of the outerwidth portion which corresponds to a maximum concavity run-out of of thetotal concavity. In a preferred embodiment, this value is furtherlimited to a maximum of /8". Referring to FIG. 2, one side of the ingotis supported at any point between the outer edge 16 and point 18 whichcorresponds to a concavity run-out y of not more than 50%, or half, ofx, or across this entire outer band, as by a belt or roller band ofsuitable width to support the side of the ingot from point 18 to point16, the other side of the ingot width being similarly supported. Thus,restating the matter, each belt 65 supports the ingot and the startingplug 74 at the outer portion of their respective widths, the supportprovided thereby not extending inward, toward the center of the ingotwidth, beyond that portion of the ingot corresponding to a mold bottomsurface run-out of 50% of the total concavity. As indicated above, it ispreferred to further limit this value, y" in FIG. 2, to /s" maximum. Thebelt support plate 68 may be wide enough to support both belts or it cancomprise two separate plates to provide separate support for each belt,although the former may be preferred in that it assures that the beltswill describe a common plane. While extensive reference to supportingthe ingot by an endless belt has been described, rollers or the like canalso be used within the scope of the invention. In the event rollers areemployed, bands may be positioned about their periphery to provide thesame support in5 accordance with the invention as furnished by the belts6 The dimensions of the belt cross-section can vary considerably in thatany thickness which permits the starting plug bottom to clear the beltsupport plate 68 will suffice. However a thickness of to /1" has beenfound to be highly satisfactory in that it is of sufficient thickness tobe used with molds having a bottom surface concavity of /2" which shouldinclude almost all ingot sizes of current commercial significance. Afabric and rubber composite belt of this thickness also generallyexhibits sufiicient resiliency to compensate for the very minorshrinkage that does occur at the outer portions of the ingot width.

The width of the belts is not particularly critical although from thestandpoint of commercial practice it is best to select a width andspacing combination compatible with as many ingot sizes as possible.This, of course, minimizes the extent of belt repositioning necessarywhen changing mold sizes. For instance, positioning two belts each 8" inwidth and A5" in thickness so as to provide a spacing or gap of about24" between the belts will accommodate most ingots having widths rangingfrom 30 to 45". However, it is obvious that many deviations can be madeto accommodate the individual circumstances posed by the particularcontinuous casting apparatus involved and those skilled in the art willhave no trouble in utilizing the invention in their particular schemes.For instance, ingot size, composition and casting speed are among thepredominate factors to be considered as will be appreciated by thoseskilled in the art.

In order to further illustrate the practice of the invenion, thefollowing example will proceed. Ingots are horizontally cast of analuminum base alloy having a nominal composition of 4.5 weight percentmagnesium, the balance being aluminum and incidental impurities. Theingots have a predetermined cross-section of 16" in thickness by 39" inwidth with substantially fiat top and bottom surfaces and are intendedto be used as stock in a hot rolling mill. The mold has an openingconforming to the crosssection of the ingot except that the top andbottom inner surfaces have a concavity of almost /2". Ingots are cast inan apparatus as generally illustrated in FIGURE 3 and describedhereinbefore. A fiat belt is provided to Withdraw the ingot and anoverhead hold down roller is employed to assure intimate contacttherebetween. The support belt and the bottom surface of the mold arealigned to facilitate withdrawal of the staring plug which, by the way,has a cross-section substantially identical to that of the mold openingexcept for a small peripheral gap or clearance of, say, or M Thestarting plug is inserted ino the mold and molten metal is introducedinto the molten metal reservoir and thence into the mold. Withdrawal ofthe starting plug is initiated immediately upon molten metal filling themold in order to avoid massive freezing of the metal in the mold andreservoir which would then prevent a successful casting run. The ingotimmediately adjacent to the starting plug conforms roughly to the convexsection thereof, but after a short distance of about acquires very flatsurfaces at the top and bottom. However, once this stable ingotconfiguration is achieved, the bottom surface of the ingot is disposed/2" above the support belt. This misalignment, unless compensated for asdescribed herein, causes the ingot to defleet downwardly /2" to restupon the belt. The deflection is permanent which causes the axis of theingot between the mold and support belt to be inclined downwardly towardthe belt. The ingot metal emerging subsequently must also deflectdownwardly toward the support belt surface. This creates a series ofwaves or undulations along the length of the ingot. At the end of thecasting run, it is required that surface imperfections be removed fromthe ingot in order to prepare the top and bottom surfaces for hotrolling. This may amount to a metal removal depth of only A", from thestandpoint of the alloy segregation and other surface conditions whichare intended to be cleaned up by this scalping operation. However,because of the serpentine-like undulations of up to /z" along the ingotlength, this depth must be increased to M1 on both the top and bottom toassure a substantially straight piece with proper surfaces for hotrolling. In a run in which the ingot withdrawal belt is removed from thebelt rollers and replaced with two separate belts, each in thickness and8" in width, situated so as to bear against only the outermost 6" of theingot and starting plug width, the belt surface is aligned with thepredetermined flat-bottomed ingot plane. Casting is initiated as before,and here the flat-bottomed ingot misalignment is practically nil suchthat there are no significant deflections along the ingot length. Thisingot can be prepared for hot rolling by the removal of only A" metalfrom the top and bottom surfaces as opposed to the previous practice ofremoving A. This savings in metal scrap is highly significant in acommercial operation.

While the invention has been described with particular reference to apreferred embodiment and practice, it is to be understood that theclaims are intended to embrace other embodiments and practices as fallwithin the true spirit of the invention.

What is claimed is:

1. An apparatus for the continuous casting of a metal ingot comprising ahorizontally disposed open ended mold, the inside surface of the bottommold wall exhibiting a concavity of at least A3" to compensate for nonuniform ingot contraction in the vertical dimension, a starting plughaving a cross-section to substantially match that of the mold openingsuch that it may be positioned within the mold opening to substantiallyclose the same, means for withdrawing said starting plug and the ingotconnected thereto from the mold and for supporting only the outerportions of the widths of the starting plug and the connected ingotcorresponding to those outer portions of the mold width having a maximumconcavity runout of 50% of the total concavity run-out.

2. An apparatus for the continuous casting of a metal ingot comprising ahorizontally disposed open ended mold, the inside surface of the bottommold wall exhibiting a concavity of at least A1" to compensate fornonuniform ingot contraction in the vertical dimension, a starting plughaving a cross-section to substantially match that of the mold openingsuch that it may be positioned within the mold opening to substantiallyclose the same, means for withdrawing said starting plug and the ingotconnected thereto from the mold and for supporting only the outerportions of the widths of the starting plug and the connected ingotcorresponding to those outer portions of the mold width having a maximumconcavity run-out of 50% of the total cavity run-out, but not to exceed/8 3. The apparatus according to claim 2 wherein the supporting meanscomprises one or more endless belts.

4. The apparatus according to claim 2 wherein the supporting meanscomprises two endless belts each positioned to support one side of theingot width.

5. The apparatus according to claim 2 wherein common means are providedfor withdrawal and for support of the starting plug and ingot.

6. The apparatus according to claim 2 wherein separate means areprovided for withdrawal and for support of the ingot and starting plug.

7. The apparatus according to claim 2 wherein common means provided forwithdrawal and for support of the starting plug and ingot are integral.

8. The apparatus according to claim 2 wherein separate means areprovided for withdrawal and for support of the ingot and starting plug.

References Cited UNITED STATES PATENTS 944,668 12/1909 Douteui 22-57.22,121,280 6/1938 Bell 2257.2 2,890,560 6/1959 Nigelli et al. 198343,250,376 5/1966 Griner et al. 19835 FOREIGN PATENTS 200,324 11/ 1955Australia.

531,090 10/ 1956 Canada.

WILLIAM J. STEPHENSON, Primary Examiner. R. D. BALDWIN, AssistantExaminer.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No 3 ,349,837 October 31 1967 Kenneth J. Brondyke et al.

It is hereby certified that error appears in the above numbered patentrequiring correction and that the said Letters Patent should read ascorrected below.

Column 4 lines 58 and 72 for "5/6", each occurrence read 5/8 column 6lines 43 and 46 for the claim reference numeral "2", each occurrence,read l line 50 before "provided" insert are Signed and sealed this 26thday of November 1968.

(SEAL) Attest:

EDWARD J. BRENNER Commissioner of Patents Edward M. Fletcher, Ir.

Attesting Officer

1. AN APPARATUS FOR THE CONTINUOUS CASTING OF A METAL INGOT COMPRISING AHORIZONTALLY DISPOSED OPEN ENDED MOLD, THE INSIDE SURFACE OF THE BOTTOMMOLD WALL EXHIBITING A CONCAVITY OF AT LEAST 1/8 TO COMPENSATE FORNONUNIFORM INGOT CONTRACTION IN THE VERTICAL DIMENSION, A STARTING PLUGHAVING A CROSS-SECTION TO SUBSTANTIALLY MATCH THAT OF THE MOLD OPENINGSUCH THAT IT MAY BE POSITIONED WITHIN THE MOLD OPENING TO SUBSTANTIALLYCLOSE THE SAME, MEANS FOR WITHDRAWING SAID STARTING PLUG AND THE INGOTCONNECTED THERETO FROM THE MOLD AND FOR SUPPORTING ONLY THE OUTERPORTIONS OF THE WIDTHS OF THE STARTING PLUG AND THE CONNECTED INGOTCORRESPONDING TO THOSE OUTER PORTIONS OF THE MOLD WIDTH HAVING A MAXIMUMCONCAVITY RUNOUT OF 50% OF THE TOTAL CONCAVITY RUN-OUT.